Mix stock, sugar, sherry and soy sauce. Wash the meat, dab dry and cut into large cubes. Clean, wash and cut the peppers into pieces. Peel onions and cut into slices.
Put the meat, peppers and onions on 8-10 skewers. Marinate in the marinade for about 24 hours. Take out skewers and dab dry. Grill on the barbecue for about 10 minutes all around.